1. Field of the Invention
The present invention relates in general to an apparatus for displaying sensed electrical information and in particular to a solid state indicator for displaying electrical information in an analog form of decimal notation.
2. Description of the Prior Art
The two basic means for displaying electrical information are the electro-mechanical meter and the solid state display. In the electro-mechanical meter, the electrical energy is converted into the movement of a mechanical pointer across a meter face carrying indicia of the quantity being displayed. In the solid state display, an analog-to-digital conversion takes place to generate drive signals to activate segments of the display to form letters, numbers and symbols. These segments can be in the form of gas discharge tubes, liquid crystals, light emitting diodes, etc.
One form of prior art solid state display is a light bar comprised of a plurality of individual display segments arranged in a straight line. Each segment represents one predetermined portion of the total display, such as one percent. Each segment is driven from a comparator which compares the input signal level with a reference voltage from a voltage divider. Such a device has the disadvantages of being difficult to read from a distance and requiring a large number of segments for reasonable resolution.
Another solid state indicating device is disclosed in U.S. Pat. No. 4,199,758 issued to Wilhelm et al. In this indicating device, a plurality of LEDs representing the decades information are positioned in a semi-circle and a second plurality of LEDs representing the units information are positioned in a straight line. Such an arrangement results in improved readability. However, the Wilhelm et al. device utilizes discrete electronic components which results in increased costs and relatively extensive circuit calibrations.